New methods have been developed using negative ion electron capture chemical ionization gas chromatography-mass spectrometry (EC/CI GC-MS) for the assay of the norepinephrine (NE) metabolites, 3-methoxy-4-hydroxy phenylglycol (MHPG), dihydroxyphenylglycol (DHPG), normetanephrine (NMN) and metanephrine (MN). These methods increase the sensitivity of detection methods permitting the study of NE metabolism in much smaller amounts of biological material than was previously possible.